A Ni-base alloy, a Co-base alloy or the like is known as this type of heat-resistant alloy, but in recent years, improvement in thermal efficiency has been strongly demanded for the purpose of improving fuel economy and reducing environmental burdens of various heat engines and improvement in heat resistance of constituent materials of the heat engines has been more severely required. For this reason, development of novel heat-resistant materials alternative to the conventional Ni-base or Co-base alloy has been studied and many research reports have been published.
For example, the present inventors have disclosed an Ir—Al—W-based alloy, which is an Ir-base alloy, as a new heat-resistant alloy alternative to the Ni-base alloy (Patent Document 1). This heat-resistant alloy uses a precipitation strengthening action of a γ′ phase (Ir3(Al, W)) which is an intermetallic compound having an L12 structure as a strengthening mechanism of the heat-resistant alloy. Since the γ′ phase exhibits inverse temperature dependence such that strength increases with a rise in temperature, the γ′ phase can impart excellent high-temperature strength and high-temperature creep characteristics to the alloy. Note that the use of the strengthening action of the γ′ phase is similar to that in the conventional Ni-base heat-resistant alloy.